Various types of LED illumination devices using light-emitting diodes (LEDs) as light sources are being developed. Examples of such LED illumination devices include downlight-type LED illumination devices and desk stand-type LED illumination devices (refer to Patent Literature 1, for example).
For example, a typical LED illumination device includes: a light-emission module including a plurality of light-emission parts each of a different color temperature; an optical member that is a lens, a reflection member, etc., disposed on an optical path of light emitted from the light-emission parts; and a lighting circuit for lighting light-emission elements included in the light-emission parts. Each of the light-emission parts includes: a light-emission element that is an LED. In addition, each of the light-emission parts includes a wavelength conversion member that is disposed so as to cover the light-emission element. The wavelength conversion member includes fluorescent material, and converts some light emitted from the light-emission element. Light emitted from each of the light-emission parts is provided with a desired color temperature by mixing the light emitted from the light-emission element and the wavelength-converted light output from the wavelength conversion member. For example, a typical LED illumination device whose light color is adjustable includes a light-emission part of an incandescent lamp color, which corresponds to a color temperature of around 2500 Kelvin (K) on the black body curve, and a light-emission part of a daylight color, which corresponds to a color temperature of around 8000 K on the black body curve. Note that in the present disclosure, the unit K (Kelvin) indicates a correlated color temperature. Further, in the context of the present disclosure, the term “correlated color temperature” is used for both correlated color temperatures on the black body curve and correlated color temperatures that are not exactly on the black body curve.
When driving the LED illumination device and adjusting the color temperature of the illumination light from the LED illumination device to a desired color temperature, the light-emission part of the incandescent lamp color and the light-emission part of the daylight color are caused to light simultaneously, and the color of the light emitted from the light-emission part of the incandescent lamp color and the color of the light emitted from the light-emission part of the daylight color are mixed. By mixing the light colors of the different light-emission parts, the color temperature of the illumination light from the LED illumination device is adjustable within a wide range of color temperatures from approximately 2500 K to approximately 8000 K.